1. Field of the Invention
This invention relates to a universal joint for connection drive and driven members in which the drive and driven members during operation are subject to a substantial degree of angular articulation and to compressive loads therebetween. Specifically, this invention relates to a universal joint for an automotive tilt steering system.
2. Description of the Prior Art
Various prior art patents disclose universal joints in which power or torque is transmitted from a drive member to a driven member by a plurality of spherical roller balls which are engaged partly in recesses in an inner member and partly in rectilinear recesses in an outer member, one of the inner and outer members being a part of or connected to the drive member of the joint and the other of the inner and outer members being a part of or connected to the driven member of the joint. U.S. Pat. Nos. 4,425,101 to Krude and 2,910,845 to Wahlmark illustrate such universal joints, and U.S. Pat. No. 4,156,354 to Krude illustrates a universal joint in which the torque transmitting bodies are partly spherical.
In universal joints of the type described, the centers of the balls lie in a plane which is at a right angle to the central axis of the inner member, and this plane will also be at a right angle to the central axis of the outer member when the axes of the inner and outer member are aligned. During times when the inner and outer member are not aligned, the plane of the centers of the balls will move away from its position at a right angle with respect to the central axis of the outer member, an inherent requirement and characteristic of an articulating joint, and this will cause the balls to roll in the recesses of the outer joint. However, this will reduce the distance by which one of more of the balls extends into its or their respective recesses. When the recesses are uniform in depth, as is noted in the aforesaid patents, at some point in the articulation of the joints, typically of the order of 8.degree. in each direction from the aligned position of the joint members, the penetration of the balls in the recesses of the outer member will be reduced to the point where the joint will lose its metal to metal contact between the elements of the joint and substantial looseness will develop in the joint and will detract from the smooth operating characteristics of the joint.
Certain applications for universal joints require that the joint be capable of maintaining its smooth operating characteristics over a much wider range of articulation than the approximately 8.degree. that can be provided by the prior art joints of the type described. For example, tilt-steering arrangements for automotive steering systems are subject to articulation of the order of approximately at least 35.degree., and when a universal joint is to be used in such a steering system, it must be capable of maintaining its smooth operating characteristics even when it is articularted by such a degree of magnitude. Additionally, in an automotive tilt-steering system, a universal joint is used to transmit rather low levels of torque when compared, for example, to a front wheel drive joint for an automobile. Thus, it is important that a tilt-steering universal joint be rather small and relatively inexpensive to manufacture.
U.S. Pat. No. 3,424,473 to Morgan discloses a tilt-steering system which utilizes a universal joint. Apparently, the problem of reduction of ball penetration into the recess of the outer member of the joint at high degrees of joint articulation is recognized to some extent in this patent because the ball engaging recess in the outer member of the joint, in the plane of articulation of the joint through such recess, appears to be in the configuration of the arc of a circle of a fixed radius rather than in the configuration of a straight line. U.K. Patent Application No. 2,115,523 to Krude discloses a universal joint with a curvilinear recess in the outer joint member and U.S. Pat. No. 4,070,872 to Krude discloses such an outer joint ball engaging recess configuration in a four ball universal joint. In a joint of the type depicted in the U.K. Patent Application and in U.S. Pat. No. 4,070,872, it is necessary, because of the restricted openings at the end of the outer joint members, to machine the recesses in the outer joint which adds to the cost of the universal joint when compared to a joint in which the recesses can be formed by cold forming.
The circular configuration of the outer ball engaging recesses of the universal joints of U.S. Pat. Nos. 3,424,473 and 4,070,872 does not represent an optimum or even a near-optimum configuration, however, because, as a result of torque or otherwise, one of the balls in the inner member of the joints tends to stay in contact with one of the recesses of the outer joint thereby compounding the tendency of the other ball or balls in the inner member to pull away from the top or tops of their respective recesses in the outer member of the joint during the articulation of the joint.